


A BIG Problem

by Vexatious



Series: Swapfell: Mutt in Heat [3]
Category: Undertale (Video Game)
Genre: Aftercare, Alternate Universe - Swapfell, Alternate Universe - Underfell, Alternate Universe - Underswap, Biting, Bondage, Breeding, Come Inflation, Creampie, Cuddling & Snuggling, Ecto-Genitalia (Undertale), Ecto-Penis (Undertale), Ecto-Vagina (Undertale), Exhibitionism, Explicit Language, Explicit Sexual Content, Fisting (mention), Knotting, M/M, Masturbation, Mating Cycles/In Heat, Multi, Multiple Partners, Oral Sex, Overstimulation, Possessive Behavior, Sexual Exhaustion, Swapfell Papyrus - Freeform, Swapfell Sans, Underfell Papyrus, Underfell Sans, Underswap Papyrus, Underswap Sans, Vaginal Fingering, Vaginal Gaping, Voyeurism
Language: English
Status: Completed
Published: 2017-11-25
Updated: 2017-11-25
Packaged: 2019-02-06 14:20:40
Rating: Explicit
Warnings: No Archive Warnings Apply
Chapters: 1
Words: 6,031
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/12819387
Author URL: https://archiveofourown.org/users/Vexatious/pseuds/Vexatious
Summary: Can anything satisfy Mutt’s uncontrollable dominant heat? Four universes of skeletons are about to find out…





	A BIG Problem

**Author's Note:**

  * For [damnedxfate](https://archiveofourown.org/users/damnedxfate/gifts).



> Undertale Sans is referred to as Comic. Undertale Papyrus is simply Papyrus. Underfell Sans and Papyrus are Red and Edge/Boss respectively. Underswap Papyrus is Stretch. Underswap Sans is Blueberry or Blue. The Swapfells are Blackberry or Black (Sans) and Slim or Mutt (Papyrus).  
> Be sure to check out my [Tumblr](http://vex-bittys.tumblr.com)!

Papyrus waited until all of the skeletons arrived before he knocked on the Swapfell skeleton brothers’ front door. Admittedly, he’d been surprised to receive a call from Blackberry, but when the standoffish Swapfell Sans had requested his help, the Great Papyrus couldn’t refuse. As per Blackberry’s directions, Papyrus had gathered his own brother as well as their Underswap and Underfell counterparts before venturing into Black and Slim’s dangerous Underground. Comic, despite his shortcuts, showed up last as usual.

Papyrus rapped sharply on the door, but the skeleton who opened it looked nothing like the fierce, arrogant Blackberry he knew. Shadows underlined the diminutive Royal Guard’s sockets, and torn, dirtied clothing replaced his usually pristine attire. Marrow dripped from a ragged slash in Blackberry’s collar bone. Papyrus stared in shock. What had happened to Blackberry… and where was Slim? None of the other skeletons had seen one Swapfell brother without the other before.

Scanning the group of skeletons waiting outside his home to assure himself that they were all present, Blackberry tiredly invited them inside. The rest of the skeletons shuffled into the home, curious, but Papyrus couldn’t contain his concern.

“WHERE’S YOUR BROTHER? DID SOMETHING DIRE OCCUR?”

Six pairs of worried eyelights settled on Blackberry. How could he tell these skeletons what he’d done? How could he expect them to help him? He knew they considered him a friend, and in any other universe, friends could request help from each other. This was Swapfell though. Monsters didn’t form meaningful bonds like friendship. The close relationship that Blackberry and Slim shared was something they’d fought to forge and painstakingly hid from everyone. Trust meant showing weakness. Asking for help meant admitting weakness. In their world weakness meant certain death, yet these skeletons had left their respective homes to assist him without explanation or promise of reward.

Still, if there was a monster besides his brother that Blackberry could rely on, it would be one of these six alternate versions of them.

“I fucked up,” Blackberry said softly. Nobody else spoke; not a single eyelight would meet his… except for Papyrus. The tall skeleton gestured for Blackberry to continue speaking, features locked in a stoic non-expression. Blackberry steeled himself to explain the events that led up to their impromptu meeting.

“Mutt went into a dominant  heat cycle last week. I decided it might be interesting to… deny him… for an extended period of time, a strategy to enhance the eventual gratification of release.” Oh, how Blackberry had built the anticipation, chaining Mutt to the wall in the basement, parading in front of him in scanty lingerie. Blackberry had teased his brother, spreading himself so that Mutt could see him, smell him. Mutt had whimpered and begged, raged and thrashed to get at his Lord while Blackberry had touched himself, always just out of his brother’s reach.

 

It had been agonizing for both of them. Mutt’s frustration left him gasping in pain after each intense session of provocation, but Mutt loved a heavy dose of suffering with his pleasure. The scent Mutt emitted during his heat drove Blackberry insane with desire, ensuring his erogenous magic remained summoned, slick with arousal and burning with sensual heat. Even the time he spent pleasuring himself in front of his brother to torment him wasn’t enough. Only one thing would truly satisfy him- unleashing his lustful Mutt. His plans had gone badly awry when he entered the basement last night to free his brother. Mutt had already gotten loose.

“Last night, when I went to check on him-”  _(to remove the chains and let him force my face into the floor and fuck me into oblivion)_  “-there was… a problem. A big problem. Mutt wasn’t himself. I couldn’t control him; he didn’t even recognize me. I managed to get him locked into the cage.” Blackberry’s eyelights vanished completely as he relived flashbacks of using blue magic  _(ineffectually!)_  and bone attacks to drive his crazed brother back into the cage, locking him in with shaking hands as tears welled in his sockets.

“You locked your brother in a cage?” the scandalized voices of the Swap and Tale skeletons asked, appalled at the imprisonment.

“YOU  _LOCKED_  YOUR BROTHER IN THE CAGE, RIGHT?” Edge asked, grateful that the imprisonment would make Slim more manageable.

“wait, what yer sayin’ is that your bro’s in heat? that’s it? fuck, the way you were actin’ we thought Slim dusted or something.  what… you need us to hold ‘im down while you give him a  _hand_?” Red’s mocking words hid the snarl rolling from Blackberry’s mouth, but Edge saw the flash of blue-purple eyelights, flaring with intent to harm. He quickly stepped between Blackberry and his brother. Thwarted, Blackberry paced.

Of course these skeletons didn’t understand.

“If Mutt had dusted, none of you would be here,” Blackberry explained in a low growl. “I would have avenged him then dusted myself. Mutt isn’t just in heat, as you so casually put it, Red.” Blackberry spat the Fellverse Sans’ name. “He has lost himself. I put his collar on him as a sign that I would always take care of him, that he could trust me to put his interests first and foremost. I failed… and I might not be able to undo this. I only hope he will return to his senses once his heat is satisfied… and my body is not strong enough to satisfy him on my own.”

During Blackberry’s speech, Blue had sidled over and put a comforting hand around his darker twin’s waist.

“How can we help?” Blueberry’s voice was uncharacteristically quiet.

“His heat must be dealt with, but at this point… “ Blackberry let the sentence trail off.

“HIS LASCIVIOUS APPETITE HAS BECOME INSATIABLE?” Papyrus ventured. Every skeleton present was aware of Slim’s voracity and stamina, and all Papyruses had extreme heat cycles. No wonder Blackberry doubted his ability to handle Slim by himself.

Blackberry nodded.

 

“eh, what’s a hardcore pounding between friends, right?” Stretch commented offhandedly.

“Actually,” mumbled Blackberry, “my brother prefers smaller partners.” His soul twisted in his ribcage. The other skeletons frequently intermingled their relationships, but Blackberry and Slim mostly kept themselves separate. Blackberry would never go to another monster for his sexual needs, but what about Mutt? What if his brother decided he wanted to be with someone else? What if he got Mutt back only to lose him to one of these other skeletons?

Comic finally spoke: “so just us Sanses, huh? i guess i’m down for that.”

Red added a sulky “i’m in.”

“The Magnificent Sans is here to help!”

Blackberry exhaled, a soft sound of relief. “Follow me.”

* * *

 

Slim’s tall, lanky body collided noisily with the bars of the cages, rattling steel and bones as he slobbered and snarled, trying to reach Blackberry. His eyelights smoldered, several shades darker than usual and completely unfocused. What had once been a black tank top and navy boxers could now only be referred to as tatters as they hung in shreds from his hunched body.  A collective gasp rose from the visiting skeletons, but Blackberry’s eyes were locked on his brother. He’d done this to Mutt. Guilt clawed at him.

Six sets of sockets widened as their corresponding eyelights drifted down Slim’s body. The delayed gratification of his heat cycle had left the already well-endowed skeleton with a massive erection decorated with a thick knot at its base. Precum dribbled from the engorged member the moment the door to the basement opened.

“WE SHALL HAVE TO PREPARE OUR BROTHERS,” Papyrus said into the vacuous, shocked silence. He, Stretch, and Edge began to undress their smaller brothers while Blackberry continued to stand motionless. Soon the sound of breathy moans began to fill the space. Mutt growled hungrily as he drank in the scent of arousal, his own smoke and citrus heat aroma permeating the basement and stirring up the other skeletons’ ecto-bodies. Each pair of skeletons reacted to it differently.

Papyrus, with his impeccable control, and Comic, with his lazy indifference, were the least affected by Slim’s heat. Comic draped himself limply across his brother’s lap while Papyrus fingered him slowly and steadily. Edge and Red, whose relationship most closely resembled the Swapfells’, were sequestered in a corner, speaking in low voices. Edge, the duo’s dominant member, forced his fingers in and out of his brother’s plump little pussy hard and fast.

“JUST REMEMBER, RED: WHATEVER HE DOES TO YOU, I WILL DO TO YOU LATER, ONLY A THOUSAND TIMES BETTER.” Red who preferred the submissive role whimpered and moaned his brother’s chosen title, Boss, over and over, bucking his hips so that Edge’s fingers could reach deeper inside of him.

Stretch lacked the restraint of the other Papyruses. He had Blueberry on his back on the floor, mewling, with his tongue buried in his brother’s tight, trembling pussy. Blue’s eyelights had morphed from eager stars to hazy hearts as Stretch gulped down his gushing juices, swirling his tongue farther and farther into Blue’s warm, wet cunt, looking for more. Blue’s small hands clutched Stretch’s skull as he writhed against his brother’s ministrations.

“Don’t make him cum,” Blackberry admonished Stretch. “You don’t want him to get overstimulated.”

Stretch’s face emerged from between Blueberry’s ample ecto-flesh encased femurs. The tall skeleton’s tongue darted out to swipe at the sheen of glossy blue arousal smeared across his mouth and chin. He breathed heavily, obviously wanting more of his little brother, but he respected Blackberry’s words.

“What about you?” asked Blueberry pointedly, waving a now unoccupied hand at Blackberry. “You can’t possibly take a cock that size dry…”

Blackberry never stopped staring at his brother. “I did this to him. I failed him. I don’t deserve mercy.” Blackberry had removed his clothing while the other skeletons were distracted, and Blue could now see the tracery of bite marks on his neck and shoulders and bruises on his spine and hips from his encounter with Slim the previous evening. Blackberry didn’t seem to notice the injuries or care, and he obviously felt that he deserved no absolution for his actions, but…

 

Blueberry stood up and moved close to Blackberry, reaching a small, delicate hand around to carefully part his Swapfell counterpart’s folds. “Slim would never forgive himself if he hurt you. Don’t make it worse for him when he regains his senses just because of your own guilt.” Blueberry slid two phalanges into Black, working diligently to stretch the other skeleton’s narrow hole. Blackberry leaned against Blue, allowing himself the briefest of moments to enjoy the sensation of Blue’s fingers stroking and curling inside his hungry, aching walls.

Too soon, Blackberry pushed Blue’s hands away from his body. He’d waited long enough. The time had come to set things right with Mutt.

“INSTRUCT US,” the stalwart original Papyrus proclaimed. Blackberry took up his mantle as a Captain of the Royal Guard and began issuing orders.

“Each of us will take a turn until Mutt cums or we say the safe word, which will be ‘Snowdin.’ The Papyruses will subdue Mutt with blue magic while we switch places. It will likely take two of you using blue magic simultaneously to properly hold him. He is… not himself, so I think it would be best if we used the breeding station.”

“you have a breeding station?” Stretch sounded more intrigued than surprised.

“Of course,” huffed Blackberry, levelling his blue-violet gaze at his brother and remembering his excitement when he’d shown Mutt the new toy. Nothing thrilled Blackberry more than complete helplessness. Once the sheepskin-lined leather cuffs were securely fastened, holding him bent over the padded stand, he surrendered himself to Mutt’s control, to be used as his brother saw fit. They’d spent many long nights relieving the stress of their lives with that exhilarating role reversal.

“Papyrus, please secure me to the breeding station. Mutt will be… enthusiastic when you release him.” Blackberry grabbed the keys to the cage from his shorts and tossed them to Edge, who caught them neatly from the air. “Just open the lock and stand aside.”

Blackberry walked over to the unusual appliance, positioning his body onto it carefully and deliberately to demonstrate the most comfortable stance, and Papyrus bound his wrists and ankles tightly into the restraints. Seeing Blackberry bent over and exposed, mixed with the heady pheromones exuded by Slim, made Papyrus want to take Blackberry then and there, but his resolve didn’t waver. He resisted the temptation. Slim, on the other hand, had his quarry in his sights. His darkened eyes gleamed with a predatory light as he panted and prowled in the confines of his kennel.

When Papyrus stepped away and nodded to the Edge, the tall Underfell skeleton unlocked the cage and let the door swing wide. Consumed by carnal instinct, Mutt let out an animalistic growl as he exploded past Edge towards his brother. Blackberry barely recognized Mutt under his feral demeanor, but he didn’t have time to think about it because Mutt mounted him immediately, slamming into him without any warning or even the courtesy of gradual entry.

The lancing pain of the invasive penetration quickly faded into an intense, ardent pleasure that turned Blackberry’s initial scream into a desperate lustful moan. Blackberry felt full, so full as his magic tried to contain his brother’s immense cock. His stomach bulged, rubbing deliciously against the padded cushion beneath it with each forceful thrust. Blackberry’s tight little hole couldn’t even take his brother’s full length, though Mutt didn’t seem to care as he pounded into him, hands braced on Blackberry’s hips to steady his brother as each forward motion of his hips shook the breeding station.

 

Suddenly, a damp pressure slid up Blackberry’s spine. Mutt’s tongue traveled up Blackberry’s vertebrae, between his shoulder blades and to the base of his neck. The watching skeletons all flinched at the sound of sharpened teeth crunching into bone as Mutt bit into his brother deeply enough to leave a permanent mark.

“YOU’LL BE KEEPING YOUR COLLAR ON, RED,” hissed Edge. “I WON’T ALLOW HIM TO MARK YOU.” Red stared with open desire at the rough treatment, and Blackberry’s mewling cries had Stretch pulling Blue into his lap to rub gentle circles around his palpitating entrance.

With his teeth sunk into his brother’s neck, Mutt made a final brutal thrust, shoving his cock and its knot all the way into his brother’s squelching cunt. Blackberry’s magic stretched and swelled, pushed past the comfortable limit as he screeched at the fiery sensation of being fisted by the knob at the base of Mutt’s cock.

Blackberry’s pussy clamped down on Mutt’s length as cum poured into him with every pulse of the thick member. As the euphoria of orgasm overtook him, his eyelights rolled back in his head. His tongue lolled from his mouth, spilling saliva down his chin as Mutt continued to shallowly thrust, causing Blackberry’s magic to swell with the sheer amount of his brother’s seed within him. Black’s own fluids gushed with the intensity of his orgasm, but Mutt’s knot kept their mingled magic from escaping.

“I THINK IT IS TIME WE INTERVENE,” commented Papyrus to the other awestruck skeletons.

“i’m next,” Red declared, despite Edge’s menacing glare.

“LET’S RESCUE BLACKBERRY FIRST.” Papyrus noticed that Slim was still rutting against his brother as they dawdled. Comic teleported out of the room and returned almost instantly with some blankets from an upstairs closet. Edge, irritated by his brother’s behavior, turned Slim’s soul blue with a sharp PING!.

Slim didn’t stop slamming into Blackberry, who still moaned lewdly as his tongue flopped with every thrust. Stretch added his magic to Edge’s, and together the two tall skeletons managed to drag Slim away from Blackberry. Slim growled, slavered, and struggled against the magical confinement, cock still hard and knot still prominently displayed. The moment he’d pulled out, cum had gushed from Blackberry’s gaping pussy, pooling on the floor between the smaller skeleton’s feet. Blackberry’s delicate cunt had been left wide open for all to see, and Red couldn’t wait. He darted over while Papyrus was still busy removing the cuffs from Blackberry’s wrists and ankles.

Comic draped one of the retrieved blankets around Blackberry’s shoulders. Blackberry’s ragged breathing eventually slowed as he leaned against the other Sans. Meanwhile, Papyrus quickly set Red up on the breeding station. The short gold-fanged skeleton flushed at being in such a vulnerable position and sweat beaded on his skull. Papyrus would’ve been worried if he hadn’t spotted the heart-shaped eyelights and arousal-slicked ecto-flesh that gave away Red’s needy anticipation. Seeing new prey trussed up and willing, Slim strained forward, nearly snapping the tenuous blue magic that held him. Stretch and Edge hesitated only a second longer before turning him loose.

 

“i always did like doggy-style,” Red quipped, trying for a quick laugh, but Slim pounced. Red forgot every single word in his vocabulary except the occasional weak “yes” or “more.” As a dedicated masochist, Red enjoyed rough sex and overstuffing. He was no stranger to his brother skipping foreplay either, and Slim hilted effortlessly inside Red’s hot, dripping cunt with one savage buck of his hips. Edge scowled at the blissful expression on his brother’s face.

The slap of hip bones against plump ecto-flesh punctuated Red’s hysterical begging. The throbbing knot at the base of Slim’s cock caught and dragged at Red’s tender slit, and the larger skeleton soon leaned forward with a grunt and a growl to bite down on Red and dominate him completely. The collar did its job though; Slim couldn’t find purchase for his jaws on the smaller skeleton’s neck. Instead he dug the pointed tips of his phalanges into Red’s tender ecto-flesh, flaying the magic as he pounded in and out of the tightly gripping pussy. Hot strings of saliva from Slim’s parted jaws dripped onto Red’s scapulae like salacious raindrops.

“your brother seems to be enjoying himself,” mumbled Stretch, his mouth partially occupied by kissing his own brother’s neck.

“RED IS… DURABLE, BUT SLIM’S TECHNIQUE IS SLOPPY AT BEST,” Edge sneered, arms crossed petulantly over his ribcage.

Red’s mouth hung open, tongue dangling limply as moan after moan fell from his throat. His sockets fluttered as Slim’s grip moved from his ass to his ribs to maximize the leverage for the last few vigorous thrusts. Drool flowed freely down Red’s tongue to drip onto the floor as his eyelights sparked and flared. Slim exploded inside him so hard, so fast, so much… Red’s magic couldn’t even contain it. Cum spilled out around Slim’s knot, cascading onto the floor. Red screamed as his pussy clenched and vibrated, trying to take in all of thick, sticky load.

“RED’S DONE. HAND OVER YOUR BROTHER, ASHTRASH,” Edge snapped the moment Slim finished riding his release in Red’s twitching hole. Edge surged forward as Stretch and Papyrus used their special attacks to wrangle Slim. When Edge freed Red from the restraints, the smaller skeleton stumbled into his arms. Slim’s conjured magic remained undiminished.

“ready or knot, here i cum, Boss,” Red laughed, but he accepted the blanket his brother wrapped around him with tired gratitude. Edge sputtered irately at the ill-timed puns, but he could see Red struggling to hold his legs together as more and more of that dark orange cum spilled out of him to pool on the floor. Oh how he longed to exchange that orange magic for his own deep crimson brand.

Blueberry expertly positioned himself on the breeding station, regarding his brother with half-lidded eyes. “LIKE THIS, PAPY?” he asked in a sultry voice, wiggling his summoned ass at his brother as Stretch secured him by the wrists and ankles. Fuck, Blue looked so good bent over, pussy lips puffy, arousal slowly oozing from that extra tight, super sensitive slit.

“you sure you’re up for this, Blue?” Stretch was sure up, but that had very little to do with Slim fucking his little brother.

“THE MAGNIFICENT SANS CAN HANDLE ANYTHING!” Blue stated proudly.

The other skeletons backed away from Blueberry hastily when Papyrus and Edge dismissed their blue magic. For the third time, Slim lunged, attempting to bury himself in Blueberry’s cunt the way he had done to Blackberry and Red. Blueberry was simply too tight. Determined, Slim mounted the smaller skeleton, pushing in inch by inch, chuffing with desire as the heat and dampness enveloped him. Every time Slim rocked his hips, Blueberry emitted a breathy “Mweh.”

Panting and clutching at Blueberry’s hips with a crushing grip, Slim finally bottomed out inside of the smaller monster. Blueberry’s magic stretched and pulled so far he felt like he might break, and tears gathered in the corners of his sockets. Stretch had prepared him too well, and at the first movement of Slim’s cock inside of him, Blueberry came, sending juices gushing from his cunt onto Slim’s robust knot.

“PAAAAAAAAPY!” wailed Blueberry as his pussy walls vibrated and flexed around the too-large member filling him.

 

Hearing his brother scream his name in the throes of ecstasy proved to be too much for Stretch. He reached into his cargo shorts and palmed his own aching erection, pumping it roughly while Slim began thoroughly fucking his mewling brother. Slim set a punishing pace, chasing more and more of the friction from Blueberry’s cunt squeezing his throbbing length.Tears streamed down Blueberry’s face as the sensation of the knot pushing into him overwhelmed him.

Stretch jerked himself hard and fast.

“ARE YOU MASTURBATING TO YOUR BROTHER GETTING FUCKED?” Edge asked disdainfully.

“don’t pretend you weren’t hiding a  _bone_ -r while he railed Red,” Stretch countered before turning to Blackberry, who had recovered from his session with his brother already. “do you think Slim would mind if i put Blue’s mouth to use?”

Blackberry chuckled darkly. “If you approach his mate during a dominant heat, he’ll dust you, whether it’s  _your_  brother or not.”

“shit.” The revelation sobered Stretch, but he didn’t stop stroking himself. He couldn’t. Not with the expression of unadulterated lust on Blue’s face, not with Blue’s unfocused heart-shaped eyelights, not with Blue screaming his name over and over as he came completely undone from the savage pounding. Stretch just wanted to cram his cock down his brother’s throat so that Blueberry was getting fucked from both ends. Such a waste not to see that round, sweet face painted with honey-colored cum….

The slick from Blueberry’s first orgasm spattered with each snap of Slim’s hips. Blue felt like the thick cock was tearing him apart, and he loved it. He couldn’t stop moaning Stretch’s name. His eyelights were rolling back, and he felt his pussy clamp down on Slim’s shaft, putting pressure directly on that exquisite, cunt-destroying knot. Slim bowed his spine, lowering his skull to Blueberry’s neck, inhaling deeply. Slim’s jaws closed around the dainty bones without piercing them as Slim braced himself for a final mighty thrust, emptying his bulging knot for the third time.

Blue screamed his brother’s name as his taut pussy struggled to accommodate the flood of hot cum expanding the limits of his magic to the precipice of distress.

Stretch gasped as Blue’s amorous screams drove him to release as well. Pale orange cum shot from Stretch’s cock in thick ropes, making a complete mess of his khaki shorts and the one area of the basement that had remained somewhat clean.

Since Blueberry’s brother was too preoccupied to help, Papyrus and Edge used their magic to drive Slim away from the smaller skeleton. Surprisingly, once Slim had withdrawn from him, Blue whimpered unhappily. “More… please… don’t stop…” he murmured, dazed by lust as his cunt contracted in a third orgasm, forcing a seemingly endless stream of mixed dark orange and pale blue magic to spurt from his battered pussy with each spasm.

Not bothering to tuck his still-hard cock back into his pants, Stretch hurried over to help Blueberry off of the breeding station, but when he got to his brother, he couldn’t resist admiring Slim’s handiwork. The lanky, gold-fanged skeleton had split Blue wide open; Stretch had never seen Blue’s luscious little pussy spread so beautifully before. He held up a hand next to the heaving, cum-leaking opening. Fuck, he could fist his brother right now, just fuck the smaller skeleton with his whole fucking arm until he passed out from the blinding pleasure of it.

Stretch sighed. No. He couldn’t indulge himself. Blue and Black had, by far, the most stamina of all the Sanses, and, from the look of Slim- or rather, his unwavering erection, his libido was nowhere near satisfied.

Still, the sight of Blueberry’s freely drooling mouth lodged thoughts of sloppy blowjobs, swallowing, and facials firmly in Stretch’s mind. He’d ignore those urges for now, but once they went back to their own universe? He’d spend the next week erasing every memory of his Swapfell twin from his brother’s mind and body.

 

Instead of wasting valuable energy walking, Comic simply teleported the scant few feet to the breeding station. He draped himself lazily over the apparatus, waiting for his brother to fasten the cuffs to hold him in place. Blackberry wondered if the manacles were even necessary. Comic had become one with his lewd perch and already appeared to be dozing off.

“THIS ISN’T A JOKE, SANS,” Papyrus warned. Did Comic ever take anything seriously? He could be injured if he didn’t exercise diligence and caution!

“‘m just taking the relaxed approach, bro.” In fact, Comic hadn’t even bothered with an ecto-body like the other shorter skeletons had. He’d just lazily summoned a pliable opening in his pelvic inlet.

“AS LONG AS YOU’RE SURE…” Papyrus sounded uncertain.

“i’m not  _sure_ , i’m  _Sans_ ,” Comic joked. “but i’m ready to throw the mutt a  _bone_ , if that’s what you’re asking.” Papyrus called back his blue magic with an indignant groan at his brother’s puns. Slim, eager for a fresh hole to sink into, snapped Edge’s grip on his soul easily.

Slim sprang forward, plunging into Comic’s supple pussy with a wanton growl. Comic struggled to maintain his flippant facade under the onslaught of the tall skeleton’s recklessly bucking hips. Papyrus’ expert preparation techniques and Comic’s focus on quality over quantity made the smaller skeleton’s cunt equally satisfyingly tight and comfortably resilient. Slim slammed into Comic repeatedly, increasing the speed and strength of the thrusts each time. His phalanges raked the smaller skeleton’s spine, ribs, and shoulder blades as Slim drove his cock forcefully into Comic’s limber hole.

The pun-loving skeleton’s ever present smile started to come undone as his magic filled and emptied with merciless speed and bruising force. Comic couldn’t keep breathy gasps and moans from escaping him. The clack and rattle of bone against bone echoed underneath the sounds of two skeletons panting harshly. Slim and Comic wore identical expression of sex-fueled delirium- dulled eyelights, widely parted jaws, and saliva-soaked, lolling tongues. Slim’s immense knot finally slipped past Comic’s soft folds to complete their coupling.

Papyrus nodded in approval. Comic’s complete submission and relaxed body were a perfect strategy. Slim rapidly approached climax with such a prostrated partner. Slim fucked Comic like a warm, breedable cocksleeve, and when he came he roared like a victorious apex predator. Comic’s choice of minimal conjured ecto-flesh allowed the other skeleton to watch in utter fascination as Slim’s hot, thick load pumped into Comic’s swiftly burgeoning magic. With the exception of Papyrus, the other skeletons waited expectantly for the aftermath of Slim’s orgasm to cause Comic to climax as well. Papyrus knew better. Comic needed a long, slow session to build release. A hard and fast encounter like this could have only one possible outcome.

Comic let out a thunderous snore.

Blackberry stepped up beside Papyrus. “I’m ready to go again.” He tossed his blanket into the corner, eyelights tracking Mutt, who had already prowled away from Comic and advanced on his brother.

“HOW LONG DO YOU THINK HE’LL KEEP GOING?”

“I don’t know. He always stopped when  _I_  got tired before.”

* * *

 

Each Sans had taken on a second round with the insatiable Mutt, and Blackberry found himself secured to the breeding station for the third time. Stretch, Edge, and Papyrus cradled their own brothers, nuzzling necks, whispering words of praise, and rubbing their stomachs, distended with an influx of copious amounts of dark orange cum. The foreign magic swirled inside them in such a high amount that their own magic couldn’t absorb enough of it to dissipate. Red and Comic slept contentedly, and Blueberry lethargically returned his brother’s affectionate gestures.

The moment Edge and Papyrus freed Mutt, he mounted his Lord again. Mutt’s entire length, knot included, slid easily into his brother now. Blackberry’s insides burned from overstimulation, and instead of gratifying friction, every thrust tore at his chafed and tender pussy. Blackberry’s neck and shoulders were heavily mottled with marrow-weeping bitemarks, and Mutt’s thick, slobbering tongue lapped at them hungrily even as he dug his fangs into damaged bones to create new ones.

Blackberry could only utter soft groans and whimpers as he suffered through the agony of Slim fiercely fucking his too-sensitive cunt. The bolts that held the breeding station to the basement floor rattled with the motion of Mutt;s thrusts, and Blackberry gritted his sharp teeth to ride out the hellish experience. He was doing this for Mutt. He’d do anything for Mutt, even let his brother ravage him until he dusted. At this point, with unbearable pain coursing through his very soul, that ending seemed inevitable.

“BLACKBERRY DOESN’T LOOK SO GOOD,” Blueberry observed in a worried tone.

“I FEAR HE IS TOO STUBBORN AND PROUD TO USE THE SAFE WORD. HE BLAMES HIMSELF FOR THIS SITUATION AND BELIEVES HE MUST SUFFER WITH NO RELIEF.” Papyrus’ response was grim but true.

Mutt’s phalanges tore grooves in the ecto-flesh of Blackberry’s ass as he hammered his brother’s abused pussy brutally with his girthy, knot-adorned cock. Tears and drool flowed freely from Blackberry’s sockets and mouth, but he refused to utter the word that could make it all stop. He owed this to Mutt.

Suddenly the tension drained from Blackberry’s body. The small skeleton’s jaw fell slack, and his eyelights flickered out. Oblivious, Mutt continued to pound his brother’s limp, unconscious body.

“STOP HIM!” shouted Papyrus, and Edge and Stretch’s sockets flared with magic as they strove to subjugate an unsatisfied Slim. Blueberry pulled Red away from the scuffle.

“NOW WHAT?” snapped Edge, snorting aggressively with exertion.

“I WILL HANDLE SLIM.” Papyrus had already stripped and tossed his clothing aside. His smooth, pale bones gleamed, and his lush orange magic looked particularly enticing. “WHO BETTER TO SATISFY A PAPYRUS THAN A PAPYRUS?”

“do you think he’ll go for it? i thought Blackberry said Slim preferred Sanses?” Stretch asked softly.

“THERE IS NO OTHER CHOICE. BLACKBERRY AND OUR BROTHERS ARE EXHAUSTED AND CAN’T TAKE ANY MORE PUNISHMENT. IT IS NOW UP TO THE GREAT PAPYRUS!”

“need any ah… help… before you go?”

“THE GREAT PAPYRUS DOESN’T NEED FOREPLAY! JUST MAKE SURE TO COLLECT BLACKBERRY AS SOON AS I ENGAGE SLIM!”

Papyrus sauntered up to Slim, making sure he held the gold-fanged skeleton’s focus before motioning for Edge and Stretch to liberate him. Slim shoved Papyrus up against the wall, rutting into the tight, unbroken cunt between Papyrus’ femurs. Papyrus actually reached behind him to guide Slim’s cock into his waiting hole, arching his back slightly to give the Swapfell skeleton a better angle for penetration. Slim accepted the invitation and buried his length in the other skeleton.

Stretch and Edge crept over to the breeding station. Edge watched Slim and Papyrus while Stretch unlatched Blackberry’s bindings. Without the restraints to hold him in place, Blackberry slumped to the floor, and Stretch gathered the small frame into his arms. A hand on Stretch’s hoodie yanked him backwards abruptly. Stretch stumbled, dropping Blackberry, but the lazy skeleton’s sockets widened at the sight of the bone spears that impaled the space he’d been standing. Edge continued to drag Stretch away from Blackberry, fending off bone attacks as they retreated.

“WE’LL HAVE TO WAIT TO RETRIEVE BLACKBERRY.” Edge stated the obvious. Just as Blackberry had explained, Slim would not allow his mate to be taken from him.

Papyrus took advantage of Slim’s distraction and swept his legs out from under him in a neat wrestling move that Undyne had shown him. The two tall skeletons tumbled to the floor, and Papyrus engineered the fall so that he ended up on top. Slim’s fingers scrabbled at Papyrus’ strong arms as the original pinned him to the floor and began to lower his dribbling pussy onto Slim’s engorged cock, all the way down onto the knot. Seating himself with his spine gently arched and his legs spread on either side of Slim’s hips, Papyrus began to ride the other skeleton hard.

“WHO DO YOU THINK WILL LAST LONGER?” mused Edge as Papyrus lifted and lowered himself, gyrating his lumbar region to maximize the pleasure for himself and his partner. Slim’s struggles had morphed into tightly gripping Papyrus’ iliac crests as he rocked his own hips upwards.

“i’ll put 50g on Slim.”

“YOU MUST LIKE THROWING MONEY AWAY, ASHTRASH. IT’S A BET.”

Slim’s pace stuttered, and Papyrus slammed himself down to take the whole load. Papyrus didn’t relent after a single orgasm like the others had done. He kept moving, riding Slim even harder with no reprieve in sight. Slim growled and panted as he matched Papyrus’ furious pace, his knot already swelling as his next climax built. Papyrus wrapped his hand around the developing knot and squeezed, milking a second orgasm from Slim before the afterglow even faded from the first.

Slim resented the more dominant attention and hooked one of Papyrus’ ankles, flipping them over. Handling Papyrus roughly, Slim grabbed him and threw him to the floor on his stomach. Sensing the desired position, Papyrus lifted his tailbone towards the ceiling, wiggling his greedy cunt temptingly at Slim. As Papyrus suspected, Slim simply wanted to top. With a snap of Slim’s hips, his thick, twitching cock was sheathed in a trembling pussy once more.

 

Papyrus and Slim tussled and fucked for over three hours. Edge and Stretch called the shots like sports announcers and cheered like spectators. Finally, Slim’s movements stilled. Papyrus rubbed his pussy along Slim’s length for a few seconds longer, just to be sure, but the gold-fanged skeleton was spent at last.

“PAY UP,” demanded Edge. Stretch handed over the money. Honestly, watching the stamina test of the century had been worth it.

Papyrus stood up, brushing himself off. The only sign of his ordeal was a slight wobble to his first few steps towards Comic. Movement across the room caught Papyrus’ eye, and he paused. Slim, utterly exhausted and barely able to move, crawled over to Blackberry. Touching the smaller skeleton with a hesitant finger, Slim rasped:

“M’Lord?”

The sound of Mutt;s voice made Blackberry curl in on himself. “M-Mutt?” Mutt wrapped his entire body around Blackberry’s, pulling his brother close and holding him pressed securely to his ribcage. The gesture was clearly one of protection rather than possession.

“LET’S TAKE OUR BROTHERS UPSTAIRS TO REST,” suggested Papyrus. “I THINK THEY’D RATHER BE ALONE RIGHT NOW.”

Stretch hefted Blueberry into his arms, bridal style. On their way out the door, Papyrus distinctly heard Stretch suggesting that he and Blue acquire a breeding station for themselves. Blueberry agreed drowsily.

Edge grabbed Red around his waist and lugged him up the stairs like luggage. “REMEMBER WHAT I TOLD YOU, RED! I’LL MAKE YOU SCREAM JUST LIKE THAT EXCEPT LOUDER AND LONGER!”

“sure thing, Boss,” Red chuckled.

Papyrus swaddled his brother in one of the soft blankets from earlier. Before he turned off the light and closed the basement door, he checked on the Swapfell skeleton brothers one last time.

They laid together on the floor, slumbering peacefully, with Blackberry tucked firmly against Slim’s body. Only eyes as sharply observant as Papyrus’ would’ve spotted the two monster souls showing in the narrow space between their ribcages. One soul was blue-purple; one was dark orange, and they beat together in a perfect, soothing rhythm.

It looked like the Swapfell brothers would be just fine after all.


End file.
